1 Answer
1

This patch adds new calling conventions to ctypes foreign functions by
passing 'errno=True' or 'GetLastError=True' to the CDLL or WinDLL
constructor.

If CDLL(..., errno=True) or WinDLL(..., errno=True) is used, the
function objects available in the CDLL or WinDLL instance will set the
C global errno to zero before the actual call, and attach the C global
errno value after the call as 'errno' attribute to the function
object. This attribute is stored in thread-local storage.

This doesn't really clear up the difference. I used this feature initially and it doesn't work without also being used on the function prototypes, so the difference is critical to answering this question.
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Matt JoinerOct 23 '11 at 22:45